TMEV-induced demyelinating disease is a highly relevant model for multiple sclerosis (MS) in which epidemiologic evidence strongly indicates involvement of an environmental factor, probably a virus infection. Thus, Investigations into the pathogenesis of this experimental animal model may well provide insight into MS. Virus-cell receptor interactions are a major determinant of virus host specificity, and the identification of specific virus receptors has greatly increased our understanding of viral pathogenesis. It is also apparent that many viruses use more than one cell surface molecule for their attachment and cell entry. The overall goal of the proposed research is to elucidate the molecular basis of Theiler's murine encephalomyelitis virus (TMEV) infection primarily at the level of attachment and cell entry, and to relate this to the persistent infection in mice. These studies should provide new insight into the mechanisms underlying TMEV persistence. They plan to: (1) Characterize the recently identified TMEV receptor protein, UGT, which mediates cell entry and infection of viruses of both TMEV neurovirulence groups. UGT is a member of a family of intrinsic membrane nucleotide-sugar transporter proteins resident in the trans-Golgi network (TGN). Vesicles bud from theTGN and cycle to the plasma membrane, so it is likely that UGT is expressed on the cell surface. These experiments will entail: (a) Demonstrating surface expression of UGT in transfected R26 and other somatic cells. (b) Analyzing the level of UGT mRNA and protein expression in different cell lines and mouse tissues. (c) Determining the sequence of the mouse homologue. (d) Identifying the TMEV binding site on extracellular domains of UGT by competitive inhibition with peptides, mAbs and insertional mutagenesis. (e) Determining whether UGT:(chromosome 11, 56.0 cm) is Tmev-5, a recently reported genetic locus mapped at 52.0 cm on chromosome 11. Tmev-5 is responsible for clinical disease and possibly viral load in (C57BI/6 X 129Sv IFN gamma-/-) F2 mice. (f) Determining the molecular basis of the functional loss of UGT activity in receptor-negative BHK-21 clones. (2) investigate the effect of sialic acid binding by less virulent TMEV on neurovirulence and viral persistence as well as determine the molecular basis of this receptor interaction. (3) Investigate whether the DA virus L*-1 mutant is reduced in fitness, since it has never been shown that acute CNS virus growth in mice by L*-1 mutant is comparable to that of wild type DA virus.